GRB 050402
GCN Circular 3172
Subject
Very questionable identity of Swift-BAT GRB050402 (Trig=113225)
Date
2005-04-02T15:45:36Z (21 years ago)
From
Scott Barthelmy at NASA/GSFC <Scott@lheamail.gsfc.nasa.gov>
S. Barthelmy, L. Barbier (GSFC), J. Cummings (GSFC/NRC),
E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (UMD),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS),
M. Suzuki (Saitama), J. Tueller (GSFC)
on behalf of the Swift-BAT team:
At 06:09:55 2-April-2005, UT Swift-BAT triggered on a marginal event
(trigger=113225) which has been reported as GRB 050402 (GCNs 3167, 3168,
3169, 3170). The BAT team believes that the automated notice sent out earlier
is likely consistent with a noise fluctuation, but we can not absolutely
rule out that it was due to a very soft, weak GRB. The reasons which make
this a questionable detection are: (a) detected only in the 15-25 keV band,
(b) the image significance is very marginal, and (c) the noise in the
detector array is slightly elevated during this interval (thus increasing
the chance coincidence of a rate fluctuation and an image-domain fluctuation).
GCN Circular 3169
Subject
GRB050402: XDSS counterpart
Date
2005-04-02T09:02:51Z (21 years ago)
From
Derek Fox at CIT <derekfox@astro.caltech.edu>
Derek B. Fox and S. Bradley Cenko (Caltech) reports on behalf of a
larger collaboration:
"We note that the IR afterglow candidate of Chen et al. (GCN 3168) has
a point-like counterpart in second-generation Digitized Sky Survey
(XDSS) i-band (n-emulsion) images. The source is also detected close
to threshold in R-, I-, and z-band imaging from P60. Analysis as to
source variability is ongoing."
GCN Circular 3167
Subject
GRB 050402: Early observations with Swift-UVOT
Date
2005-04-02T08:02:08Z (21 years ago)
From
Patricia Schady at MSSL/Swift <ps@mssl.ucl.ac.uk>
S. T. Holland, M. Still (GSFC/USRA), W. Landsman (GSFC), Adam Morgan, S.
Hunsberger (PSU), A. Breeveld (MSSL), P. Roming (PSU), K. Mason, P. Schady
(MSSL), M. Ivanushkina (PSU), T. Poole (MSSL), C. Gronwall (PSU),
A. Blustin (MSSL), P. Brown (PSU), S. Rosen, K. McGowan, M. De Pasquale (MSSL),
P.Boyd, S. T. Holland (GRFC/UMBC), H. Huckle (MSSL), P. Broos (PSU), T.
Kennedy, P. Smith, B. Hancock (MSSL), H. Krimm (GSFC/USRA), S. Kock (PSU),
M. Carter (MSSL), K. Gendreau (GSFC), M.Chester (PSU), D. Hinshaw
(GSFC/SPSYS), J. Nousek (PSU), N. Gehrels (GSFC), on behalf of the Swift
UVOT team.
The Swift Ultra-Violet/Optical Telescope (UVOT) began observing the field
of GRB 050402 at 06:12:01.6 UT, approximately 125 seconds after the BAT
trigger. The first image was sent down via the TDRSS link approximately
300 seconds after the trigger. This image was a 100 second exposure taken
with the V filter. It was centred on the BAT position, and had a size of
5 x 5 arcminutes, which covered 88% of the BAT error circle. The image was
binned 8 x 8 to reduce the bandwidth required for transmission. A
comparison against the DSS showed no new sources down to a 5-sigma
limiting magnitude of approximately V = 18.84 +/- 0.09 , based on
preliminary in-orbit zero points.